Many pull-on diapers use elastic elements secured in an elastically contractible condition in the waist and leg openings. Typically, in order to insure full elastic fit about the leg and the waist such as is provided with durable undergarments, the leg openings and waist opening are encircled with elasticized bands of rubber or other materials positioned along the curve of the opening. Examples of such pull-on diapers are disclosed in EP 1 184 012 A1 published on Mar. 6, 2002. The pull-on diaper disclosed therein comprises an absorbent body and an exterior member covering the absorbent body and forming a contour of the diaper. The absorbent body is substantially rectangular and comprises a liquid-permeable topsheet, a liquid-impermeable backsheet and an absorbent core interposed therebetween. The leg and waist elastic members are installed into the exterior member to form an elasticized leg opening and an elasticized waist opening. The longitudinal sides of the exterior member are trimmed to form a leg opening. While trimming the longitudinal side of the exterior member allows to form a desired shape of curved leg opening, it requires an additional process for trimming and wastes raw materials.
Another example of pull-on diapers is disclosed in Japanese Laid-open Publication No. H4-144558 published on May 19, 1992. The pull-on diaper disclosed therein comprises an absorbent main body and an elastic belt joined to the front region and the back region of the absorbent main body. The elastic belt extends in the transverse direction of the diaper and the absorbent main body extends in the longitudinal direction. The upper end of the elastic belt defines a waist opening. The lower end of the elastic belt and the longitudinal side of the absorbent main body jointly define a leg opening. The elastic belt disclosed therein comprises a front belt and a back belt which have the same longitudinal length between the upper end and the lower end. While such a front belt configuration allows the diaper to fit the wearer's body between the front thigh and the abdomen, the back belt having the same longitudinal length between the upper end and the lower end as the front belt does not cover the wearer's buttock to the extent that the diaper appearance looks like a real garment.
Based on the foregoing, there is a need for a disposable pull-on garment effectively covering the wearer's buttock at the back while allowing a snug fitment at the front.